Prime Minister Kevin Rudd said there was overwhelming evidence of the use of chemical weapons against civilians by the Syrian regime.

Speaking at a press conference in Brisbane on Wednesday, Mr Rudd said the government was working ''very closely with our partners, our friends and allies across the world at this time of growing crisis in the Middle East and Syria in particular''.

''Let us not forget what has happened here,'' Mr Rudd said.

''What we have is tantamount to a crime against humanity, when you see the use of chemical weapons against civilians.

''We have high confidence that the regime in Syria is responsible.''

Mr Rudd said it was incumbent on the prime minister at such a time of international crisis to be in touch with world leaders.

''‘When you are looking at our responsibilities on the UN security council, it is critical that we are in close contact with other members,'' he said.

Mr Rudd said Australia's ambassador to the United Nations, Gary Quinlan, would take up Australia's presidency of the security council on Sunday.

''The diplomatic activity in New York is now at full speed and it is important that the international community form a common resolve on this question,'' he said.

But Foreign Minister Bob Carr said Australian troops won't be sent to Syria in the event of a military intervention by Western forces.

Senator Carr is also convinced Assad forces were behind the attack.

''A government that uses chemical weapons against its own people has to be made to pay a price,'' Senator Carr told a business conference in Perth on Wednesday.

''The evidence accumulates that this chemical weapons attack did take place and came from the Assad forces.''

Senator Carr said the preference would be for a United Nations-sanctioned action, but if that was not possible, ''the sheer horror'' of the attack mandated a response.

But internet whistleblower Julian Assange, Senate candidate and leader of the WikiLeaks Party, has declared his opposition to an Australian-supported military intervention into Syria in the absence of a ''proper and full investigation'.

In a telephone interview with ABC radio on Wednesday morning, Mr Assange said that, if elected, he would oppose any motion in the Senate to engage the Australian military in the Syrian conflict without further evidence, stressing the importance of knowing who was responsible for the attacks before deciding upon a course of action.

''If it's the rebels, if it's a breakaway commander exceeding his authority or if it's an authorised act by the Syrian Government, these lead to different outcomes,'' Mr Assange said.

He cited the Iraq War as a cautionary tale that demonstrated why ''important decisions about war should be made on clear evidence as to what happened and clear evidence as to what an outcome would be''.

Mr Assange added that any military action must contemplate an exit-strategy, as well as a consideration of inevitable refugee flows and loss of innocent life.

Labor has pledged to consult the Coalition on any major policy decisions on Syria during the caretaker period of the election campaign.

Australia could become the voice of international condemnation over the situation in Syria, as the president is given the job of briefing the world's media on the council's deliberations.

That job is likely to fall to Mr Quinlan - or Mr Rudd himself, should he decide to go to New York and chair the council meeting, as he is entitled to do.

Western nations all but accused Bashar al-Assad's regime of culpability in the chemical attack, believed to have left hundreds dead.

On Tuesday, Mr Rudd warned of a ''humanitarian disaster''and said he had spoken with US President Barack Obama about the conflict.

''The international community is increasingly concluding that chemical weapons were used, and that the Assad regime is, in all probability, responsible,'' Mr Rudd said.

''If true, this would be crime against humanity and a violation of international law. It would not be without consequence.''

His tough language matches that of the US, Britain and France, while Russia remains more circumspect. China also holds a Security Council veto.

The prospect of military action appears to rest on the findings of a team of UN inspectors sent to the site of the alleged chemical attack, only to come under sniper fire.

Mr Rudd has also spoken with his British counterpart, David Cameron, about how to react to an alleged chemical weapons attack in Syria.

A Downing Street spokesman says both leaders agree that it’s increasingly likely the Syrian regime is responsible for the attack.

The spokesman says the prime ministers talked of the need for a serious international response to the attack, and that they’d keep in touch over the coming days.

A Downing Street statement released after the phone call says: ‘‘The world cannot stand idly by in light of such a significant chemical weapons attack.’’